Late Pop III Star Formation During the Epoch of Reionization: Results from the Renaissance Simulations

TL;DR

This study uses high-resolution cosmological simulations to show that Population III stars can form late during the epoch of reionization due to local metal enrichment and radiation effects, revealing new insights into early galaxy formation.

Contribution

First detailed simulation-based analysis of late Pop III star formation at high redshift, highlighting the roles of local metal enrichment and radiation feedback.

Findings

14 Pop III galaxies identified at redshift 7.6

Late Pop III formation due to slow metal enrichment and radiation suppression

A Pop III star cluster similar to CR7 but less luminous

Abstract

We present results on the formation of Pop III stars at redshift 7.6 from the Renaissance Simulations, a suite of extremely high-resolution and physics-rich radiation transport hydrodynamics cosmological adaptive-mesh refinement simulations of high redshift galaxy formation performed on the Blue Waters supercomputer. In a survey volume of about 220 comoving Mpc$^3$, we found 14 Pop III galaxies with recent star formation. The surprisingly late formation of Pop III stars is possible due to two factors: (i) the metal enrichment process is local and slow, leaving plenty of pristine gas to exist in the vast volume; and (ii) strong Lyman-Werner radiation from vigorous metal-enriched star formation in early galaxies suppresses Pop III formation in ("not so") small primordial halos with mass less than $\sim$ 3 $\times$ 10$^7$ M$_\odot$. We quantify the properties of these Pop III galaxies and their Pop III star formation environments. We look for analogues to the recently discovered luminous Ly $\alpha$ emitter CR7 (Sobral et al. 2015), which has been interpreted as a Pop III star cluster within or near a metal-enriched star forming galaxy. We find and discuss a system similar to this in some respects, however the Pop III star cluster is far less massive and luminous than CR7 is inferred to be.